The invention relates to the crowns of tires and especially to the cushion compounds in contact with the cords that reinforce these crowns.
The crowns of tires usually comprise a carcass reinforcement, belting, usually with at least two reinforcing plies, and a tread. These crowns are in contact with the ground and transmit to the wheels, via the sidewalls and the beads, the transverse forces necessary for steering the vehicles. For the on-road behavior of the vehicles to be satisfactory, it is necessary for the crowns to be very rigid relative, for example, to the sidewalls. An on-going goal is to attempt to obtain this kind of high rigidity simply and in the most economical way possible.
It is well known that the cushion compounds that bind the reinforcing cords of the belting play a part in obtaining a high rigidity. This is why these cushion compounds usually have a high modulus of elasticity. By contrast, the cushion compounds for the carcass cords usually have a low modulus of elasticity because they need to withstand without damage the high amounts of deformation they experience in the sidewalls of the tires.
Furthermore, there is a great deal of research currently being carried out in an attempt to reduce the fuel consumption of road vehicles. To this end, the desire is to design tires which have a very low rolling resistance while keeping the other properties, namely of wear, adherence, behavior, etc. the same, and to do so in the most economical way possible.